1. Field of the Invention
This invention relates to a threaded child resistant closure. More particularly, this invention relates to a two-piece child resistant closure.
2. Related Prior Art
There is a large variety of threaded child resistant closures utilizing a two-piece cap in which an inner cap threads onto the container neck, and an outer cap contains the inner cap in a nested relationship. The outer cap is manipulated to engage the inner cap so that when the outer cap is turned the inner cap is threaded onto or unthreaded from the container neck. There may be separate engaging elements on the inner and outer caps for unthreading or opening the closure and separate elements on the inner and outer caps for closing or threading the closure onto the container neck. These opening and closing elements may also be combined, and various devices can be used to allow freewheeling of the outer cap in the unthreading direction until the outer cap is manipulated to engage the inner cap.
A number of these closures require the simultaneous pushing or pulling of the outer cap toward or away from the inner cap and container neck while a rotary motion is applied to the cap. Other closures require simultaneous squeezing when unthreading.
Typically, threading the closure onto the container neck requires little or no manipulation or axial thrust to be exerted on the outer cap. When the outer cap is rotated in an unthreading direction without the impartation of an axial thrust, it freely turns with respect to the inner cap and container neck. This freewheeling can be created in the drive mechanism between the caps with a ramp element on one of the caps over which the engagement element on the other cap rides in the unthreading direction. Simultaneously application of an axial force to the outer cap while turning engages these elements or other elements to impart an unthreading torque to the inner cap.
U.S. Pat. Nos. 3,705,662; 3,830,390; 4,353,474 and 4,371,088 are examples of precision molded, two-pieced push and turn child resistant closures to which the features of the present invention can be directed. Like many child resistant closures, moderate force must be used to engage the off drive, and when the closure has been solidly closed, considerable rotational torque may also be needed. With an elderly or arthritically impaired adult, such an impartation of force and/or the exercise of special dexterity can be extremely vexatious or impossible. It is to the solution of this problem that the present invention is directed.